Syntheses, characterization, and crystal structures of two zinc(II) carboxylates containing pyridine

Two organic-inorganic hybrid compounds [Zn2(mu-4-OBz)4(py)2] center dot 0.5CH3OH (1) and [Zn(2-Cl-OBz)2(py)2] (2) (OBz = benzoate; 2-Cl-OBz = 2-chlorobenzoate; py = pyridine) have been synthesized from aqueous methanol at room temperature and characterized by analytical, spectroscopic, and single-crystal X-ray diffraction. Compound 1 crystallizes in space group P21/c and exhibits a dinuclear paddle-wheel-like structure with ZnZn separation of 2.9602(7) angstrom. Zn-O distances in 1 range from 2.0272(18) to 2.057(2) angstrom and Zn-N distances are 2.043(5) and 2.004(9) angstrom. Each Zn has a square-pyramidal geometry bridged by four carboxylates in the basal plane with the pyridine at the apex. The dinuclear unit also contains 0.5 methanol. Compound 2 crystallizes in space group P1 and consists of discrete molecules having a distorted tetrahedral environment around zinc; 2-chlorobenzoate and pyridine are monodentate. The observed Zn-O distances in 2 are 2.0255(19) and 2.0377(18) angstrom and Zn-N distances are 1.9535(14) and 1.9587(16) angstrom. Weak C-HO and - stacking interactions between 2-chlorobenzoate and pyridine are operative in the crystal lattice of 2. Complex 2 on excitation at 340 nm exhibits luminescence at room temperature arising probably due to intraligand -* transition.